PROJECT SUMMARY/ABSTRACT Senescent cells, and the senescence-associated secretory phenotype (SASP), are now widely accepted as drivers of aging and multiple age-related diseases. Pre-clinical mouse studies have demonstrated that targeted removal of senescent cells has beneficial effects on cardiac, vascular, metabolic, neurological, renal, pulmonary, and musculoskeletal functions in mice, including improvements in mobility, frailty and longevity. Therefore, the selective elimination of senescent cells or inhibition of the SASP are promising therapeutic approaches to treat age-related diseases in humans. Development of these therapies requires molecular markers to identify, quantify, and examine senescent cells from human tissues. The overall objective of this proposal is to apply unbiased, quantitative, and robust spectrometry approaches to develop secreted and cell surface biomarkers for targeting, isolating, and quantifying senescent cells in humans, and to perform the first phenotyping on intact senescent cells isolated from human tissues. In AIM 1, a SASP database will be created and secreted biomarker candidates of senescence burden in humans will be identified by applying modern quantitative proteomic technologies. In AIM 2, senescence-specific cell surface markers will be identified and used to isolate, phenotype, and treat endogenous senescent cells from human tissues. The proposed work, and the resources and methods developed as a result, will have a positive impact on the translation of senescence-targeted therapies into humans by identifying potential senescence biomarkers in humans, creating translationally relevant and personalized approaches to study senescent cells, and providing fundamental insights into the biology of senescent cells in humans in vivo. The work proposed in this career development award will be carried out by Dr. Natan Basisty, PhD, a postdoctoral fellow at The Buck Institute for Research on Aging, a highly regarded academic research institution that focuses on the biology of aging. Dr. Basisty will be performing career development activities such as attending conferences and workshops, presenting his research, publishing papers, and searching for faculty positions while he carries out the proposed work at The Buck Institute for the first two years of this award under the mentorship of Professors Birgit Schilling, Judith Campisi, and Luigi Ferrucci. Dr. Basisty will leverage this award toward obtaining a position as an independent investigator doing research on the biology of aging at an academic research institution by the end of the second year, after which he will independently continue the work proposed in AIM 2 and apply for his own additional research grants by the fourth year of this award.